The objective of this proposal is to perform one additional year of follow-up data collection in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) in order to accrue the number of events required to preserve the power of the study. SCD-HeFT is a multicenter randomized clinical trial of prophylactic amiodarone or implantable defibrillator therapy versus conventional heart failure medical therapy in patients with Class II or Class III heart failure, an ejection fraction equal to or <0.35, and no previous sustained ventricular arrhythmias. NHLBI funding for the trial was awarded for a six-year period beginning May 1, 1997 and ending April 30, 2003. Patient enrollment in the trial began September 16, 1997, and was completed July 18, 2001, upon reaching the target enrollment of 2,500 patients (final enrollment is 2,521). Patient follow-up is on-going, and under present funding timelines, will have to be terminated by October 31, 2002 to allow time for closing out the trial, completing the study database, analyzing the data, and preparing the main trial reports before funding expires. In the original study plan, the six-year timeline for the trial included 2.5 years of patient recruitment and 2.5 years of subsequent follow-up. Despite a three-fold increase in the number of clinical sites, and numerous creative recruitment strategies, patient enrollment required nearly four years. If the original timeline for closing the study is maintained, the average length of follow-up will fall short of the originally planned average follow-up by at least one full year. The key concern is that the number of events required to achieve an appropriate level of statistical power will not have occurred. An additional year of follow-up will allow the study to accrue the number of events that are consistent with the original design of the trial, improve the precision for assessing the true effects of these interventions, and thereby provide the clinical and scientific community with therapeutic information urgently needed for the rapidly growing population of heart failure patients.